If you are going to use CO2 I don't think you want to do what you have drawn in the diagram. That way as soon as your CO2 is emmitted it will be carried out of the grow room. The second diagram is exactly what you need, but the question is, is the room going to stay cool enough? If not the only other suggestion I can think of is to rig up the smallest air conditioner you can find in a way that recirculates the air in the room and takes none from outside. Just a thought. Hope this helps and let us know how things progress. I have been interested in using CO2 also and I too would have the same problem you are having.

TGT
Tom Green Thumb Reviewed by Tom Green Thumb on . Ventilation? help me! If you saw on my "temp increasing" my grow room temp has been increasing. i have direct ventilation from out side right now ( pics below) but i want to use venting pipes to air cool my lights and so i can start using CO2. i put all my plants under one light (1000w mh) instead of two and turned the other one off. this decreased my temp by almost 10 F and now they are around 75F. I need to know if i should have one pipe going through both lights and sucking air from the ceiling or if i should Rating: 5